


Ulterior Motives

by raregloves



Category: Sherlock (TV)
Genre: Cunnilingus, Double Penetration, Established Sally/Sherlock, Multi, Mycroft stalks via CCTV, POV Mycroft Holmes, PWP, Rimming, Sibling Incest, Threesome - F/M/M
Language: English
Status: Completed
Published: 2014-06-20
Updated: 2014-06-20
Packaged: 2018-02-05 11:42:55
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 6,044
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1817290
Author URL: https://archiveofourown.org/users/raregloves/pseuds/raregloves
Summary: <blockquote class="userstuff">
              <p>Life becomes interesting for Mycroft when his brother and Sally Donovan discover they have some… mutual interests.</p>
            </blockquote>





	Ulterior Motives

**Author's Note:**

> Prompt: Not sure if your rarefic extends to threesomes? I've been pondering what a Mycroft/Sally/Sherlock fic (okay smut) might look like and keep drawing a blank which might be because I'm trying to keep them In character (though I do have a Mycroft/Irene/Sherlock bud I'm nurturing). Mycroft POV (you write it so well) would be lovely. Perhaps some Sally/Sherlock teasing to get Mycroft hot and bothered? Kinky/non-kinky/level of smut is author's choice but I'd love it to be fun and snarky. Thanks in adv.

Mycroft examined the CCTV footage with a feeling of foreboding. This was a feeling he had started to associate with Sherlocks schemes years ago, and it had become something of a sixth sense.

The grainy footage showed Sherlock four streets away, walking alongside Sally Donovan. Her background check had come back spotless, which made her presence (and the fact that Sherlock was clearly _not_ under arrest, for once) only more suspicious. 

He accessed all the more recent footage of Sherlock on CCTV, collected by his surveillance team. Normally Mycroft would only watch if it contained something of importance: an attempt on Sherlocks life, if Sherlock lingered too long near his old, unsavory haunts… 

No, Sherlock hadn’t been doing anything blatantly suspicious. But Mycroft knew his brother, and every instinct he had was telling him that Sherlock had an awful, devilish, no-good and possibly illegal idea brewing.

All the footage of Sherlock over the past month had been collected from Baker Street and from crime scenes. Mycroft pressed his fingertips together as he watched. 

Sherlock, with John following him, entered the screen from the left. It’d been a windy day and Sherlocks jacket flapped behind him like a cloak, impressive looking even in the low quality resolution. Sally stood on the far right by the police tape. 

She spoke only briefly to Sherlock and John as they passed. It didn’t seem to be a very friendly interaction- Mycroft saw John clench his fist as he vanished off screen. Interesting. The current Sally was walking alongside Sherlock with obvious pleasure. 

The next crime scene was outside a derelict building and once again Sally stood guard by the door. She was center screen this time and checking her phone. This camera had been of better quality, and Mycroft took a moment to notice the way the cut of her skirt emphasized the length of her legs. 

No, no, he was meant to be concentrating on Sherlock. Sherlock appeared at the bottom of the screen this time, walking towards Sally with his habitual (annoying) swagger. This time John did not follow him. John had probably been working, Mycroft thought. 

Sherlock and Sally stood by the door together for a full five minutes this time, talking. Arguing, if Mycroft was any judge of body language, which he was. Sally had her hands on her hips and had shifted her weight backwards. By contrast, Sherlock had puffed his chest out. Mycroft was briefly reminded of peacock. 

Their on-screen interaction ended with Sally laughing and Sherlock scowling before vanishing into the building. Clearly she had won that round. Perhaps she was as antagonistic as he was, and they were both converging on him to send him to an early grave? It wasn’t an impossible hypothesis. 

Then things became interesting. Sherlock started to linger by Sally when he arrived (or when he left) crime scenes. Was he perhaps still smarting about her laughter, and determined to get him back? Sometimes Mycroft could see John standing in the background, puzzled. 

And it was puzzling, Mycroft thought. Deeply so. Nothing could distract Sherlock when he had a case, and yet here he was, stopping and talking to Sally Donovan (neither a criminal mastermind or great genius) running his hands through his hair as if- 

No. Sherlock couldn’t possibly… 

Yet the evidence was overwhelming. Sherlock was walking at this very moment alongside Sally Donovan and smiling and _she was smiling back_. This was highly unusual for anyone amongst the Yard, even the longsuffering D.I Mycroft had spoken to on occasion. But for this to be happening in their free time? When Sherlock was not on a case? 

It could only mean one thing: fornication. 

Mycroft relaxed backwards into his chair, allowing his eyebrows to rise. How novel! How surprising! And mother would be pleased. Mycroft would make sure he was the one to break the news, just in case Sherlock said something crude. 

He watched footage of the two of them from a week ago. They were laughing together at something happening just beyond the cameras range. Sally supported herself with a hand on Sherlocks hip, and he reached down to brush his fingers over her hand before he moved on.

Well then. No doubt about it. 

That didn’t explain why they were coming to his house, though, did it? Mycroft frowned. Their coming to visit (together, no less) was as baffling as ever. Sherlock wouldn’t want his blessing. In fact after the incident with Sebastian Mycroft was surprised that Sherlock was willing to let any partner of his within a one mile radius of him…

The feeling of unease had not lifted. It sat, heavy and sinister in Mycrofts gut. He didn’t know what Sherlock was planning, but he was planning something. Years of his brothers antics had taught Mycroft not to doubt himself in this.

He watched them as they walked together. They made an attractive couple. They both had thick, bouncy hair and toothy smiles. Sherlock had always had good cheekbones too, had always been able to show Mycroft up at posh family parties. That was the advantage of having full lips, Mycroft supposed. No matter how rude you were you’d always look kissable- 

He shook the thought off before it could take hold. He’d been down that path before, thinking about Sherlock… best not to have it on his mind when Sherlock was minutes away, bringing his new partner with him. 

With that in mind Mycroft removed the video feed from his laptop and closed it. Then, feeling slightly paranoid, he locked it in his desk drawer. Sherlock had always been an awful snoop. 

(The irony of that thought was not lost on Mycroft, but he chose to ignore it.) 

He checked himself in the mirror before going to wait by the door. Making a good impression was important to him. It was too late to intimidate her in an abandoned car park but he was in his own home, after all- he had the upper hand already. How satisfying. 

Sherlock knocked five minutes later. 

‘Sherlock, Sally, such a pleasure,’ Mycroft said as he opened the door, smiling widely. ‘I do wish you’d learn to use a doorbell Sherlock, I’m sure if you just applied yourself…’ 

Sally and Sherlock exchanged a significant look before walking inside. The feeling of unease in Mycrofts stomach doubled sharply. Had that been Sherlocks _I told you so_ look? What on earth was happening? 

‘Nice place you’ve got here,’ Sally said, peering around with interest. ‘Quite posh.’ 

‘Well-’ Mycroft started, but Sherlock cut over him. 

‘How long were you waiting by the door for us? Must’ve been a while, you look dead on your feet.’ 

Mycroft tried to grind his teeth without being too obvious about it. Clearly Sally was not having any great influence on Sherlock if he could still act like a spoiled brat within seconds of walking into somebodies home. 

‘I’m Mycroft Holmes,’ Mycroft said, turning to Sally. ‘May I call you Sally?’

‘You can,’ she said. ‘You realize that Sherlock hasn’t told you my name though yet, right?’ 

‘Well,’ Mycroft smiled. ‘I do like to know all of Sherlocks friends.’ 

Sally turned to Sherlock, her eyes wide in a combination of amusement, disbelief and…? 

‘You’re right,’ she said. ‘I didn’t think it was possible. He _is_ worse than you.’ 

‘Excuse me?’ Mycroft said, giving her one of his colder smiles. ‘I think there must have been some mistake. I wasn’t aware that I was inviting the two of you into my home just to be insulted.’

‘I wasn’t aware that we were invited,’ Sally said, shrugging. 

Sherlock laughed, clearly delighted by her flippant attitude. Mycroft shot him a furious look, trying to convey with the power of his eyeballs just how unpleasant he was planning on making Sherlocks immediate future.

‘Oh don’t look at me like that,’ Sherlock snapped. ‘This is a social visit. Let bygones be bygones.’ 

‘I’ve known you since you were a baby, Sherlock,’ Mycroft said. ‘You never make social visits without an ulterior motive.’ 

Sherlock sighed, then held his hands up over his head as if he’d been caught stealing. Sally was watching him with amusement. She really was remarkably good looking- the photos in her file hadn’t done her justice. 

‘You’ve caught me,’ Sherlock said. ‘I have an ulterior motive. Happy now?’ 

‘Not yet,’ Mycroft said. He couldn’t imagine what kind of ulterior motive would’ve brought them both to him. Did they want to elope, secretly and immediately? He dismissed the idea as ludicrous. 

‘Let’s sit down,’ Sherlock said, suspiciously polite. ‘Talk things over like adults, as you so clearly desire.’

Sherlock led Sally into Mycrofts living room, throwing Mycroft a delighted smirk over his shoulder as he went. Feeling seriously wrong-footed, Mycroft followed them. 

They sat side by side at his table. Mycroft sat opposite, remembering his first ever job interview and feeling, somehow, as if that event had been much easier than the one he was about to sit through. There was a smile playing around Sherlocks lips that spelt trouble. 

‘Now, Mycroft, you already know quite a lot about Sally Donovan, and I’ve told her quite a bit about you, so I won’t bother with any dull introductions. Are we all sitting comfortably?’

Mycroft inclined his head and Sally nodded, shifting forward in her seat. Sherlock beamed.

‘Good. Now, Mycroft: have you managed to deduce why we’re here yet?’

‘I would’ve thought the answer to that was obvious,’ Mycroft said. 

‘That means no, then,’ Sally said, grinning. ‘I’ve become quite fluent in Holmesian recently.’ 

‘I’m sure you have,’ Mycroft said darkly. Far from looking embarrassed, however, Sally smirked. His feeling that he was missing a very essential part of the conversation (i.e: the subject of the conversation) peaked. 

‘That’s what were here to talk to you about, actually,’ Sherlock said. ‘Well, in a way… As I’m sure you’re at least partially aware, Sally and I used to be on less than friendly terms.’

‘He deduced my sex life in public and I besmirched his character around John, in other words,’ Sally added helpfully. ‘Go on, Sherlock.’ 

‘Yes, well.’ Sherlock looked momentarily flustered. ‘We got past that a little while ago after discovering some… mutual interests.’ 

‘I’m sure I can imagine,’ Mycroft said drily. 

‘That’s the problem though, brother dear,’ Sherlock said, leaning across the table. ‘I don’t think you can.’ 

Sherlock leaned back, giving Mycroft a calculating look before changing tact at top speed. 

‘You’d say that I’m good looking, yes? Objectively speaking?’ 

‘Objectively yes, I suppose,’ Mycroft said, cautious. ‘Why?’ 

‘And you obviously think Sally’s attractive,’ Sherlock continued. ‘I could tell you liked the look of her the moment she walked in.’ 

‘I don’t see how this is relevant,’ Mycroft said, refusing to glance at Sally to see how she was reacting. His typically unshakable poker face was slipping. The urge to throttle Sherlock from nervous mortification was strong.

 ‘A very beautiful woman,’ Sherlock said softly. He turned to look at Sally. Mycroft didn’t recognize the expression on his face. ‘And, as I said, we discovered that we had mutual… interests.’ 

Before he could respond to this Sherlock had leant forwards and kissed Sally on the mouth. She seemed unworried by this rather inappropriate display, closing her eyes and leaning forward, deepening the kiss herself. 

Mycroft knew he ought to look away, but- Sally was beautiful, and he had never seen Sherlock like this, kissing a woman, kissing gently and intimately. Mycroft was fascinated against his better judgment. 

They were, after all, a very attractive couple. 

Sally pulled away and turned, looking Mycroft right in the eyes. He looked away, hoping that he wasn’t flushing. What on earth were they doing? 

‘Yeah, he was watching,’ she said. ‘Probably has a semi under the table.’ 

‘He doesn’t,’ Sherlock said, and Mycroft looked back up, horrified. ‘But don’t worry, we can fix that.’ 

Realization washed over Mycroft in a cold wave. He grabbed the edge of the table, unsure if he would do better to shout at them both or flee the scene. Before he could do either, however, they were kissing again, Sherlocks hand coming up to squeeze Sallys breast through her shirt. 

Mycroft swallowed, distracted, frozen in place. He could hear his own pulse hammering. This explained the expressions he had glimpsed on Sallys face- 

Sherlock broke the kiss but kept his mouth close by hers as his eyes moved back towards Mycroft. 

‘Look at that,’ he said softly. ‘Classic response: flight, fight, or fuck?’ 

‘I know which one I’d rather,’ Sally said. 

‘This isn’t-’ Mycroft started, shocked. ‘I don’t- Sherlock, you are my _brother_.’

‘You’re objectively speaking very attractive brother,’ Sherlock said, grinning.

There was no point appealing to Sherlock for sanity, Mycroft realized. He turned to Sally instead, his expression imploring. What he saw didn’t seem very encouraging, however: her eyes were gleaming.

‘Surely this isn’t what you want?’

‘Oh, I know what I want,’ Sally said. ‘I’m here because I really want to be, trust me.’ 

‘It’s not even legal-’ 

‘Neither is fiddling with the CCTV,’ Sally said. ‘But that doesn’t stop you, does it?’ 

Mycroft closed his mouth with a snap. 

Sherlock leaned forwards again, placing both his hands flat on the table with an air of determination. 

‘Cut out the nonsense, Mycroft. If you were truly disgusted, if you were really outraged, you’d already have thrown us out. The fact that you’re sitting here with us, listening and watching, is all the proof we need. But if you want a bit more convincing, fine. Sally?’ 

Sally gave Mycroft a wicked smile. She began to unbutton her shirt, her chin tilted upwards in obvious defiance. He was captivated, both by the power in her expression and by the softness of her skin, the inviting dark bumps of her nipples. She wasn’t wearing a bra. 

Mycroft was briefly and desperately pleased that he didn’t have any internal video surveillance in his house. 

She smiled at him across the table she finished with her buttons and dropped the shirt onto the floor. He noticed, for the first time, the jumble of freckles over her nose. 

‘You like what you see?’ 

Sally pinched one of her own nipples, rolling it between her fingertips. Mycrofts fingers twitched here they still held onto the edge of the table. And Sherlock, who Mycroft had almost forgotten about, chuckled. Mycroft flushed. 

It became impossible to ignore Sherlock, however. He took Sallys chin in his fingertips and gently turned her head. He lowered his head until his lips brushed hers, but he did not move. Mycroft had to appreciate the artistry of it, the contrasts between them: man and woman, fair and dark, clothed and bare.

Sally moved first, leaning forwards and pressing her open mouth against Sherlocks with a sigh. He responded at once, one hand resting against her neck and the other running up her back, following the curve of her spine. Sally retaliated, reaching up to rake her fingers through Sherlocks curls. 

Mycroft realized that he was, now, half-hard inside his trousers. He started to hope that they might forget about him, that he would just be able to watch in peace. Surely they didn’t want him to join in, not _really_ - 

Sherlock broke the kiss and began to whisper into Sallys ear, careful to keep his voice low enough and his lips hidden enough to foil Mycrofts attempts at listening. She nodded, smiling.

He swallowed nervously as Sally stood up. Ignoring Sherlock entirely she walked around the table until she stood next to Mycroft who turned in his seat to look up at her. She was still wearing her trousers and shoes.

‘You’re allowed to touch,’ she said, hands on hips. ‘And I can tell you want to.’ 

‘I do,’ Mycroft said, seeing no point in lying now. ‘But…’

Sally put a hand on his shoulder. Her eyes gazed into his, curious and bold. Mycroft could not remember the last time he had wanted to touch anybody so badly. 

‘But nothing,’ Sally said. ‘You’ve got nothing to prove, here.’

‘No,’ Mycroft said slowly. ‘I suppose I don’t.’

Sally smiled. Mycroft turned his chair around so they faced each other and, taking the hint, Sally straddled him. His cock jerked inside his trousers but Mycroft ignored it, leaning forward to lap her nipple into his mouth. Sally sighed, her hands on his shoulders.

In his peripheral vision Mycroft saw Sherlock moving. He closed his eyes, unsure if he wanted to see whatever it was his brother was doing. Instead he concentrated teasing the nipple in his mouth, Sallys weight on his lap. Mycroft ran his hands up and down her back, admiring the smoothness of her skin. 

She sighed, rolling her hips against his erection. Mycroft found himself wishing they were both wearing less clothing. Her hands slid from his shoulders down to his chest and, as if having the same idea, she began to work on his tie. She undid it with ease, tossed it aside like so much rubbish, and started on his waistcoat. 

Mycroft was in such a state of distraction that he didn’t realize Sherlock was behind him until he felt another pair of hands land on his shoulders. He jumped.

‘So tense!’ Sherlock teased. ‘I can do something about that.’ 

He began massaging Mycrofts shoulders, kneading his flesh. For a moment Mycroft tensed against the touch. Sherlocks fingers were clever, however, relaxing his muscles with well-placed pressure. And Mycroft wasn’t going to pretend that it didn’t feel nice… because it did, and anyway, siblings could give each other a massage on occasion… 

‘That’s better,’ Sherlock murmured. ‘Nice and relaxed…’ 

Sally pulled off his waistcoat and stated on his shirt. Mycroft watched her as she worked, her tongue peeking out in concentration, her fingers dexterous and swift. She pulled his shirt off and threw it in the same direction that all his other clothes had gone. 

‘Those were quite expensive, you know,’ Mycroft said, breaking his long silence.

‘Poor darling,’ Sally said, running her fingertips through the scarce hair on his chest. ‘I’m sure somebody will iron out the wrinkles for you.’ 

Sherlock snorted and Mycroft sighed, too aroused to be truly annoyed. Sally leaned down and caught Mycrofts mouth in a kiss. It had been too long, Mycroft realized, since he’d kissed anybody- he felt for a few moments overwhelmed, clumsy. 

Then muscle memory kicked in. He opened his mouth wider and felt Sally smile against his mouth. Her fingers were still sliding up and down his chest, almost tickling him. The feeling of her bare skin on his was incredible. 

Sherlocks hands, too, now had access to his naked flesh. He was rubbed at Mycrofts shoulder blades, and rubbed smaller circles into his spine, paying attention to each individual vertebrate.

‘Do you like it?’ Sally asked. ‘Do you like having him touch you?’ 

Mycroft swallowed. Sherlocks hands paused, waiting for an answer. Sally kissed his cheek, kissed his ear, as if trying to encourage speech. 

‘I do,’ Mycroft said, hardly above a whisper. ‘Yes, I do.’

‘Good,’ Sherlock said, close to his ear. ‘Now we’ve gotten _that_ out of the way, can we try this on a bed?’

‘Yes, right,’ Mycroft said, trying to sound as if he’d been intending that all along. ‘I think that would be more comfortable for everyone, yes.’ 

He got to his feet, cast a sad look towards his clothes crumpled on the floor, and then led Sherlock and Sally towards his bedroom. As he walked, the various possible combinations that two men and a woman could manage together rushed through his head, all shockingly appealing. 

Sally let out a low whistle when she walked into his bedroom. He was long used to the size of his bed, but he supposed that to the outsider it might seem a little strange. 

‘So _this_ is where all the money goes,’ Sally said. ‘You entertain here often?’ 

‘Mycroft believes strongly in first impressions,’ Sherlock said snidely. 

‘You could be a little less rude, considering,’ Mycroft said, turning to face Sherlock and making eye contact with him at last. ‘It wouldn’t do you any harm.’ 

‘Ok,’ Sherlock said, walking forwards. ‘I can be nicer.’ 

Sherlock took Mycrofts face in both his hands and, before Mycroft could process what was happening, Sherlock was kissing him. Eyes open, mouth wet. He tasted like Sally, but he kissed rougher than she did, dirtier. Mycroft didn’t even try to stop him, just opened his mouth and closed his eyes. Sherlocks tongue dominated his. 

‘Oh,’ Sally said. ‘Oh Christ, that’s hot.’

Mycroft felt Sherlock smile against his mouth. This, then, was their mutual interest? He pushed the thought away, instead walking Sherlock backwards until they fell onto the bed together.

Having Sherlock pinned beneath him was as intoxicating as Mycroft had always assumed it would be. Sally climbed onto the bed next to them. Mycroft glanced over at her- she was pulling off her trousers, kicking off her shoes. She caught him looking. 

‘Undress him,’ she said. ‘I’ll help.’ 

Mycroft nodded, glancing down at Sherock for confirmation. His brother looked eminently fuckable, with his hair in disarray, his face flushed and his eyes wild. When Mycrofts eyes caught Sherlocks, Sherlock nodded. 

Mycroft pulled at Sherlocks shirt buttons. For once in a cooperative mood (would miracles never cease?) Sherlock lifted his arms above his head, giving him proper access. The buttons looked tight enough to burst without any external aid. 

Entirely naked now, Sally joined him, undoing Sherlocks cuffs and throwing the shirt away once it was free. They both went to work on his trousers, Sally pulling at his belt while Mycroft fumbled the zip, momentarily alarmed by the bulge of Sherlocks erection. 

‘Butter fingers,’ Sherlock said, looking up at him, eyebrow raised. ‘Not intimidated, are you? Should we get a ruler out?’ 

‘I am desperately looking forward to having you incoherent,’ Mycroft said. 

‘I know the feeling,’ Sally said, nodding. 

Mycroft pulled off Sherlocks trousers and pants and then (feeling rebellious) tossed them onto the ground. He felt as if he were stretching muscles that he had entirely forgotten he had. 

‘Up, up, Sally,’ Sherlock said. ‘I’m suddenly feeling rather _hungry_.’ 

Sally burst out laughing but did as he said, scooting backwards until she was resting against the headboard, legs spread. Sherlock wasted no time at all- he crawled up and buried his face in her crotch. She moaned, tossing her head back, one hand reaching down to pet Sherlocks curls. 

Mycroft realized he was still half-dressed: like Sally, he had only stripped off his upper half in the living room. They seemed too busy to give him a hand, however, so Mycroft took care of that detail himself, throwing his trousers alongside Sherlocks with a sense of finality. 

Now what, though? He was painfully and obviously aroused, but it didn’t seem right to interrupt. Unable to keep away, however, Mycroft inched forwards until he was hovering over Sherlocks head. 

It suited Sherlock, Mycroft thought, to have his face pressed between a moaning womans legs. Mycrofts hand slid up the back of Sherlocks neck, making Sherlock groan- Sally could clearly feel his voice reverberate through her, because she keened, arching her back.

‘He’s v-very- uhg- good at this, your brother-’

‘I can tell,’ Mycroft said. ‘I wonder, though, how good he would be if he were distracted?’ 

Sally opened her eyes, interested, but Sherlock refused to acknowledge the challenge, too confident to be ruffled by mere distractions. Mycroft smiled a Sally and pressed a finger to his lips. 

He moved to the back of the bed, pleased that there was enough room for him to crouch comfortably. Sally let out an ‘ _Oh_!’ of realization, but said nothing else, not giving his game away. Then Sherlock must have done something very clever, because her eyes shut tight and her head fell back. 

Well, thought Mycroft, two can play at that game. 

He rubbed his hands over Sherlocks hips, for a moment wishing his own body had the same lithe muscles and rounded arse. Sherlock parted his legs slightly, perhaps imagining that Mycroft was going to fuck him. Instead, Mycroft rubbed both his hands over Sherlocks pale cheeks, squeezing them hard, enjoying the bright imprints his fingers left. 

‘Go on,’ Sally said from the other end of the bed. ‘I want to see what he does.’ 

Mycroft realized he was going to have to have somebody update Sallys file: the woman clearly was a genius after all. 

He lowered his head and pressed a kiss on the top of Sherlocks buttock. Then, gently, he parted his cheeks with his hands until he could lick at Sherlocks pink entrance. At once Sherlocks entire body twitched. 

‘Don’t stop,’ Sally said, running her fingers through his curls. ‘Don’t get distracted…’ 

Sherlock resumed movement with a silent air of renewed determination. Sally sighed and Mycroft wet his lips. He resumed licking, alternating between flattening his tongue and teasing with just the tip. Sherlock angled his hips upwards as best he could, giving him access. 

Mycroft used his lips and tongue to open up his brother. He could feel Sherlocks breathing increase and his knees begin to shake with the effort of splitting his mind in two. Part of him desperate to moan Mycrofts name, part of him still focused on the taste of Sally and what made her sigh for him. 

He hummed, letting the vibrations travel into Sherlock, who moaned, almost braking away from Sally at last. Mycroft felt a surge of satisfaction, and reached down to give his aching cock a few pulls, easing the pressure.

Then he pressed back into Sherlocks arse, pushing his body forwards onto Sally. She moaned Sherlocks name as one of his hands crept up her chest to grip her breast. Mycroft moaned as Sherlock squeezed, and Sallys hips began to jerk upwards. 

‘No- not like this-’ Sally said. ‘I don’t want to come like this. Sherlock, move-’ 

Sherlock pulled back, nearly throwing Mycroft off the edge of the bed. His face was wet from the tip of his nose from to the bottom of his chin. Mycroft leaned forwards and licked, tasting Sally and feeling the slight roughness of Sherlocks stubble against his tongue. 

‘I want you both, at once,’ Sally said. ‘Mycroft in front.’ 

Mycroft was fairly sure his jaw was hanging open. Beside him Sherlock was almost hovering with excitement. 

‘Are you sure?’ Mycroft asked. Sally gave him a withering look. 

‘I’m pretty fucking sure,’ she said. ‘So you’d better hurry up before I change my mind.’ 

Sherlock leapt into action, diving for Mycrofts beside drawer for lube and condoms. Sally was frowning to herself, examining the shape of the bed as if trying to work out a mathematical problem, which perhaps she was: six legs, six arms, two cocks, one cunt, three arses, thirty fingers and three heads… 

His head was spinning. The possibilities seemed endless. 

‘Ready,’ Sherlock said, holding up a tube of lube and a handful of condoms. He seemed momentarily nonplussed so see them both looking so dazed and still. ‘Well, is anyone else ready?’

‘Ok,’ Sally said. ‘Mycroft, lie on your back, middle of the bed.’ 

He did so. It was strange to have both Sherlock and Sally sitting beside him, almost looming over him. Strange, but good. His cock leaked in approval. 

Sally climbed on top of him, one leg on either side of his hips. It was much more comfortable on a bed than it had been on the chair. She stroked his cock a few times, with her hand before taking a condom from Sherlock, rolling it down his length in one fluid movement. 

‘I’m going to lean forwards,’ she said. ‘So, Sherlock, you should have room behind me. Just don’t put your weight down on Mycrofts knee and brake it.’ 

‘Fine, obviously,’ Sherlock said. ‘Enough talking.’ 

‘Patience is a virtue, Sherlock,’ Mycroft reminded him primly. ‘I’m sure-’ 

But Sally hips were above his own now, and the tip of his cock was brushing against the outer lips of her cunt. He had been ignoring his own desire, so caught up in watching them together, in wanting Sally and trying to fracture Sherlocks sexual bravado. Now the reality of his own want came crashing down around him. 

Dimly, Mycroft knew that Sherlock was talking, that Sally was answering. But he could no longer focus. It’d been too long since he had been truly, enthusiastically fucked and everything else, even the thought of Sherlock lubing his finger up to prepare Sally, was fading into insignificance. 

‘You’re going to love this,’ Sally said. 

She began so sink down, slowly, slowly, biting down on her lower lip as she went. Mycroft gasped at how wet she was, her arousal combined with Sherlocks efforts had made her slick. Mycroft was glad the condom separated them, otherwise he felt he might finish embarrassingly fast. 

‘Sherlock, relax your finger,’ Sally said, pausing, then, ‘good, that’s better.’

Her hips dropped down and Mycroft shouted out. His cock was deep within her now, and his view was spectacular- he could see here his flesh parted her lips, how she stretched around him. She rose up a few inches then dropped down again. Mycroft bit down on his lip to stop himself from screaming. 

‘Lean forwards,’ Sherlock said, his voice low with desire. ‘My hand needs a better angle.’ 

Sally put her hands on Mycroft shoulders and lent forwards until their chests were nearly brushing. His cock bent forwards with her body, didn’t slip out, and the new angle must have been working for her because she moaned. 

‘Mycroft… Christ, that’s a good spot, Christ…’ 

Sherlocks head appeared next to Sallys. He smiled down at Mycroft for a second, eyes dark, before kissing the side of Sallys neck. One of his hands was behind her, the other holding him body up on the bed. ‘Third finger,’ he said. 

Sally closed her eyes. When Sherlocks third finger pushed in the clenched, making Mycrofts hips push up in response. For a moment she swayed, unsteady. Mycroft grabbed her upper arms, holding her in place. She smiled in thanks, breathless, without opening her eyes. Her face was so close now that he could’ve counted each freckle. 

She rocked backwards and forwards for a moment, cautiously setting a pace. Mycroft breathed in sync, trying to regain his control. Once Sherlock was in her too, well- he didn’t expect any of them to last. 

‘Sherlock,’ Sally said. ‘I think I’d like you to fuck me now.’

There was a slick sound as Sherlock moved his fingers away from Sally. He picked up the condoms from where Sally had dropped them, but couldn’t open them, his fingers slipping. 

‘Let me,’ Mycroft said. 

He pulled open the condom wrapper and passed the slip of latex to Sherlock, who took it with a grunt of thanks. Mycroft wished he had a better view of Sherlock rolling it on, but he wouldn’t move Sally for the world. She was quite still, rolling her hips very, very slightly. 

‘Ok,’ Sherlock said. ‘Ok.’ 

Sally let out a long, low moan that Mycroft would have mistaken for pain in another situation. Her mouth was wide open and her whole body shook, her breasts brushing up against his chest. 

‘Sally… oh god…’ Sherlock said, almost in awe. ‘Oh… oh…’

‘Move,’ Sally moaned. ‘Sherlock, move.’ 

Sherlock did. He pushed forward into her, and in turn Sallys cunt slid around his cock, the feeling almost beyond description- he could feel her breasts against his chest, nipples hard, hear Sherlock moaning, and Mycroft had never been so aroused in his entire life. 

For a few moments, though, they moved together clumsily, Sally trying to push back as Sherlocks hips moved forwards. Mycroft took a few deep breaths, then evened his own breathing out. Sherlock caught the hint at once, attempting to do the same. And then it worked- 

Breathe in, Sally took him in deeper, Sherlock pushed forward, breathe out. Mycroft could feel sweat prickling at his temples, breathe in, Sally moans were higher and higher pitched, pinned between their cocks, and Mycroft moaned at the thought, Sherlock swore, breathe out. 

Breathe in. ‘Oh god,’ Sherlock said, his voice breaking. ‘I can feel you, Myc- Sally, I’m not going to last, I need to, I need-’ 

‘Go- on- then-’ Sally chocked out. 

Sherlock fucked her then, hips snapped forward with shocking speed, pushing her into Mycroft, they all cried out and it was over in moments- Sherlock came with a huge gasp. Mycroft reached down, just able to press his fingers against the top of her cunt, seeking out of clit, wanting them to end it together. 

He found it as Sherlocks hips slowed and slid two of his fingers beside it, pressing. Sally, who hadn’t expected it, swore loudly then came as well. And feeling her cunt grip him tight as she came was the final straw for Mycroft, too.

 

~

 

It took many minutes for the three of them to become fully aware of their surroundings again. They were all panting as if they’d just been attacked, and Sherlock already looked as if he were half-way towards sleep. 

Eventually Mycroft spoke. ‘I’m not opposed to us sleeping here,’ he said, ‘but for gods sake let me change the sheets first.’ 

For a moment neither of them replied, and then Sally burst out laughing. Sherlock joined in, sounding delighted, and Mycroft sighed. He stood with a slight wince (wondered, briefly, how many muscles he’d pulled) and began yanking at the blankets. Sally got up and went asked directions for the bathroom, which he gave. Sherlock, forever childish, attempted to yank the blankets back. 

‘Please, Sherlock,’ Mycroft said. ‘Unless you want to sleep in the wet patch?’ 

Sherlock let out a truly long-suffering sigh and climbed out of bed. He made no attempt to help as Mycroft pulled up the mattress cover and replaced it with a fresh one before throwing down dry, clean bedding. 

‘You could help, you know,’ Mycroft said. ‘People would like you more.’ 

‘Helpings boring,’ Sherlock quipped. ‘Wasn’t today fun, though? Wouldn’t you like to do it again?’ 

‘I… rather would,’ Mycroft said, honestly enough, ‘as long as you and Sally are both amicable.’ 

‘I think we will be,’ Sherlock said. ‘I’d kiss you but I think you should brush your teeth first, considering.’ 

Mycroft refused to be embarrassed as he walked to the bathroom, nearly colliding with Sally as she left. She was walking in the slightly bandy-legged way of the thoroughly fucked. 

‘Sheets changed?’ 

‘Yes, though don’t thank Sherlock for that. I’ll be with you shortly.’ 

She laughed. Mycroft realized he sounded as if he was planning a conference and shrugged. Old habits did died hard, after all- he wasn’t very practiced at post shagging conversation, but he was an expert at polite negotiation. 

He brushed his teeth, giving his reflection a critical look. His hair was messier than he’d seen it in years and there were still red splotches on his cheeks. On the whole, however, he thought he looked rather good. Though he knew that could just be the endorphins speaking. 

When he returned to his bedroom Sherlock was already asleep. He looked years younger when he was resting, and Mycroft suppressed the urge to kiss his forehead with difficulty. Sally was awake, though only just, and watching him from under her eyelids. 

‘Lucky you’ve got such a big bed,’ she yawned. ‘We might not have all fit, otherwise.’ 

‘Lucky indeed.’ 

He climbed in next to Sherlock, letting his sore muscles relax into his mattress. At some point he knew he was going to have to seriously examine what the events of today would mean in the long-run. But that could wait. 

‘Sally? Are you still wake?’ 

‘Yeah…’ 

‘It was… lovely to meet you,’ Mycroft said, slightly awkward. ‘And I hope this is the beginning of a long and beneficial association.’ 

‘Is this Holmes-talk for ‘I’d like to do this again sometime?” 

‘Yes,’ Mycroft admitted. 

Sally laughed, and then yawned again. Mycrofts eyelids felt heavy. 

‘Don’t worry, Mycroft,’ Sally murmured. ‘You haven’t seen the last of us.’

‘Good,’ Mycroft said, slipping towards sleep. ‘Good.’

**Author's Note:**

> You can send me a prompt on my tumblr- I love rare pair fic :)
> 
> raregloves.tumblr.com


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